(NBC News) - With record-breaking viewership expected Monday night for the first presidential debate between Hillary Clinton and Donald Trump, few moments could have a bigger impact on who becomes the next president.

The two candidates took diametrically opposite paths to reach the stage at Hofstra University on Long Island, New York, and will lay out radically different visions for the country.

The good news for Trump, Republicans say, is that the expectations for his performance are about at rock bottom. While he's been more a more disciplined campaigner in recent weeks, he's struggled to stay on message and answer substantive policy questions. He also has never faced the bright spotlight of a one-on-one debate. His campaign, looking to reinforce his underdog image, claims he's eschewing typical debate preparations.

"Trump has a very low bar — just go onstage and don't look completely unhinged," said Ryan Williams, a GOP strategist who worked on Jeb Bush's presidential campaign. "If he's somewhat statesmanlike with his trademark bravado, he'll do fine."

Trump's chief goal is to win back voters who normally vote for GOP candidates but are concerned about his temperament and knowledge compared to past nominees.

"He doesn't have to be better than Hillary, but he is going to have to show a command of the subject matter beyond just glitzy sound bites in order to pacify some segments of the electorate," Republican consultant Ford O'Connell said.

Clinton, meanwhile, faces sky-high expectations. She's an experienced debater, having participated in nearly 40 debates since her first campaign for senate in New York 16 years ago, and has been holding marathon prep sessions at a debate camp set up in a hotel near her Chappaqua home.

Both campaigns have been furiously working the refs in an effort to set the bar against which their candidate will be judged. They're also sharply disagreed over the role the moderator, NBC News' Lester Holt, should play. Clinton's campaign says Holt should aggressively fact check the candidates in real time, while Trump's team calls for a hands-off approach.

On a conference call with reporters Friday, Clinton aides used the word "lie" more than dozen times as they argued Trump and Clinton cannot be held to the same standard.

"His level of lying is unprecedented in American politics," said Clinton communications director Jennifer Palmieri. "For the moderator to let lies like that to go unchallenged would give Donald Trump an unfair advantage."

On the Republican side, Trump questioned Holt's fairness last week and called him a Democrat — in fact, he's registered in New York as a Republican.

"I really don't appreciate campaigns thinking it is the job of the media to go and be these virtual fact-checkers and that these debate moderators should somehow do their bidding," Trump campaign manager Kellyanne Conway said on ABC Sunday.

Bottom line: If things don't go as the campaigns hope, both seem to be laying the groundwork to blame the press.

The Trump campaign has been talking down its preparations, with campaign sources telling NBC News they are not holding formal mock debates. Instead, advisers like campaign CEO Steve Bannon, retired Lt. Gen Michael Flynn, and New Jersey Gov. Chris Christie, have joined Trump for freewheeling sessions at his Bedminster, New Jersey golf resort in which they pepper him with questions and test possible debate scenarios.

One top adviser told NBC News that Trump has resisted watching videos of past debates. The candidate is concerned that too much cramming could undermine the from-the-gut style that helped him defeat 16 candidates in the Republican primaries, the adviser said.

"It's a little trite to say it, but Trump needs to be Trump," said Lee Spieckerman, a conservative commentator and Trump surrogate.

Trump has always taken pride in his ability to get under rivals' skin, and his team is looking for new angles of attacks that could throw Clinton off her game.

Clinton's team is looking to do the same, hoping to provoke an overreaction and counting on Trump's newfound discipline will collapse under pressure.

To prepare for the debate, Clinton has has been taking the opposite approach to Trump. The candidate has been poring over briefing books and reviewing game tape of Trump's past performances in sessions that stretched into Sunday. Former aide Philippe Reines is playing Trump in mock sessions, which also include top aides John Podesta and Palmieri.

Aides have coached the sometimes severe and long-winded Clinton to keep her answers concise and her demeanor sunny, sensitive to reality that this will be the first time Americans see a woman on a presidential debate stage.

"She takes the debate preparation very seriously," Podesta said on "Meet the Press" Sunday. "She respects the American public — she wants to tell them what she wants to do for them. But she has a challenge because Donald Trump is — inveterately — says things that aren't true."

Clinton's team has also grappled with the unique challenges presented by debating Trump, whose tone and even policy stances can vary widely from day-to-day. And they've tried to anticipate potentially uncomfortable wild cards he might play, such as bringing up Bill Clinton's sexual dalliances.

Democrats also think Trump, whose derogatory comments about women over the years are featured in Clinton's latest campaign, may shoot himself in the foot by bullying Clinton the same way he did his primary rivals. Clinton benefited from a moment like that during her 2000 Senate run, when Republican opponent Rick Lazio's gambit to cross a debate stage and enter Clinton's personal space backfired.

Judging by her past debate performances, Clinton will likely come armed with fresh bits of opposition research and new one-liners to catch her opponent off guard. Clinton may also cross rhetorical lines she and her campaign have stopped short of thus far, like calling Trump a "racist" or accusing him of "bribing" public officials with campaign donations.

While Trump benefits from lowered expectations, his recent behavior suggests even crossing a low bar on expectations may be more difficult than it sounds.

Last week, the Clinton campaign invited Mark Cuban, a rival billionaire who loves tweaking Trump, to the debate. It was a thinly veiled attempt to bait the Republican nominee by dangling one of his least favorite critics — and on Saturday, Trump bit into it hook, line, and sinker.

On Saturday, he responded to Cuban's invite on Twitter by threatening to bring along Gennifer Flowers, who revealed in the early 1990s that she had an affair with President Bill Clinton. He soon deleted the tweet, only to send it again, this time with the proper spelling of "Gennifer."

Within hours, Flowers posted on social media that she would attend the debate in Trump's "corner," a move that threatened to turn the event into a circus before it even began. On Sunday, Trump campaign manager Kellyanne Conway told CNN that the campaign had "not invited her formally" and there was "no plan" to mention her in the debate, while running mate Mike Pence downplayed the story. "Donald Trump is not about that," Pence said on Fox News.

Trump has also done few interviews outside of friendly outlets like Fox in recent weeks. He sounded rusty on Sunday when asked whether his charitable foundation, which New York's attorney general is looking into after a Washington Post report on its use of donations to help settle lawsuits.

"Well, I hope so. I mean, my lawyers do it," Trump told interviewer Sharyl Atkisson,when asked of the foundation had followed the law.

All the preparations and expectation-setting will fade into the background Monday night as the two candidates take the stage for what might be one of the most anticipated — and consequential — presidential debates ever.